A technique is known in related art, in which cruise assist is realized by displaying on a monitor a composite image in which a cruise assist additional line indicating a cruise-estimation vehicle width track of a vehicle is superimposed on a taken image of the vehicle periphery as disclosed in, for example, JP-A-2002-330428 (Patent Document 1).
The cruise-estimation vehicle width track of the vehicle to be fixed by an individual vehicle design or a camera design eigenvalue differs according to vehicles, and is fixed in accordance with a steering angle of the vehicle at that time. Accordingly, the setting of the cruise assist additional line (a dynamic guide line) corresponding to the steering angle of the vehicle is performed by a microprocessor having relatively abundant ability in calculation processing such as a camera controller ECU or a navigation ECU.